Q. Dear Mike: I live in a townhouse with a small back patio that gets a decent amount of sun in the morning. It’s a concrete slab, so I'm forced to use containers for all my plants. I'd like to create some type of garden but I'm not sure what types of vegetables or trees would do well in containers. Could you give me some guidance? Thanks,
Nathan Balum; Philadelphia

A. Thank YOU, Nate—even those of us what got lots of ground to grow in still love the ease and portability of containers. But the devil IS in the detail here. Most container failures aren’t due to the wrong plants being used—they’re caused by the pots themselves or what’s used to fill them. So let’s begin with my five-point primer on proper potting up. Then we’ll talk selection.

1. Make it a BIG Container!

Whether it’s a simple window box or a prodigious posse of ponderously pretty pots posed ‘pon your porch, BIGGER IS BETTER! (Sorry, guys—but all those emails you’ve been getting are true.) Large containers don’t dry out as quickly during dry spells. And hey—you’ll be able to fit more stuff inside of them too; that’s always a plus.

2. Ixnay on Your Irtday!

Garden soil may (or may not) be adequate for your in-the-ground growables, but it’s a death trap for plants in a container—especially if that soil is the nasty, heavy clay many of us have to struggle with. Instead, fill your containers with one part compost (home-made or bagged) and three parts of a loose, light, ‘soil-free’ mixture like Premier’s Pro-Mix or Fafard’s All-Purpose Mix. Bags labeled ‘seed-starting’ are almost always the right consistency. You DON’T want ‘heavy’; you want a mix that seems almost impossibly light. And don’t use any of these new mixes contaminated with chemical fertilizers and pesticides; since when are there BUGS in peat moss and perlite?!

No compost? Use a clean soil-free mix that contains natural plant food. There are a few out there in the retail world, and Gardens Alive makes a potting soil with five different organic nutrients, including compost, earthworm castings and “mealworm crap” (now there’s an ingredient you don’t see on a lot of bags…). They also use Coir, a fiber from coconuts, instead of peat.

Or make your own mix out of one part each compost, peat, perlite, and vermiculite. (Perlite and vermiculite are natural mined minerals that keep the mix light and provide lots of room for roots to grow strong.) Add one tablespoon of lime or wood ash per five gallons of mix to adjust the pH, and combine it all up in a big tub or wheelbarrow, spraying with plain water as you go to keep down the dust. Warning: Some samples of vermiculite may contain traces of asbestos fibers (naturally present in the mined deposits); I really value the structure vermiculite lends to a mix, but if you don’t wish to use it, just add more perlite instead.

3. Drainage is Essential!

Don’t fall in love with containers that don’t have drainage holes unless you’re capable of drilling some yourself. (“Crack!” goes the $40 pot!) Always check the bottoms of your containers; sometimes you’ll have to drill holes, sometimes there are plugs that must be removed. And if the bottom of a container is very flat to the ground, put it up on bricks so the holes don’t become obstructed.

4. Pretty Pots Porous; Plastic Pots Perform Preferably

Unglazed terra cotta pots look great, but their porosity (you like that woid? Classy, huh?) wicks the water from your ‘soil’ right out into the air. Plants in such pots often need to be watered every day—sometimes several times a day; and are practically guaranteed to die when you go on vacation. Terra cotta is also breakable, heavy, and can’t be left outdoors over winter. (Well, that’s not quite true; you can leave them out. They’ll just crack.) Plastic pots are lighter, less expensive, retain moisture better, laugh at winter and come in a huge variety of sizes and colors. (If you’re just stone in love with terra cotta, find plastic pots that are slightly smaller and slip them inside, where they won’t be seen.)

5. Don’t Crowd The Plants in Those Containers

One of the biggest mistakes rookies make is trying to fit a truck patch worth of plants in a ten-inch pot. Take tomatoes. Bushy, well-behaved “determinate” varieties (like most paste tomatoes) will do great in five-gallon containers—but only one plant per pot! (Trust me—you’ll get lots more love apples this way. Too many plants? Buy more pots!) Giant, indeterminate types that produce huge fruits on long vines (like Big Boy and Brandywine) need twice that big a container. (You can plant flowers and other small stuff around the edges.)

Peppers and eggplants do fine in 10-inch pots. So will long, viney things like cukes and zukes if you provide a tall trellis for them to climb. And ‘cut and come again’ stands of salad greens SHOULD be crowded close together.

Plant what you like: Position big pumpkin pots so the long vines can trellis up your deck! Frame your doorway dramatically with pretty pepper plants! Pick cherry tomatoes as they trail down from a huge hanging basket! Just remember that flowering plants like tomatoes, peppers, eggplants and the other fabulous ‘fruits of summer’ need a good amount of sun. If the hours of daylight striking your pots time out to be less than five or six, grow things like herbs, potatoes and leafy greens that don’t need as much light instead.

You also mention trees. Once again, I’ll reiterate (I’ll even repeat it too) that any plant can be grown in a pot. But Northern gardeners have to have a plan for those plants over winter. Now, you are in a big city in what sounds like a very ‘sheltered’ location (I would just say “crowded” but I’m feeling nice today), so you MIGHT be able to leave trees, roses and other long lived perennials outdoors in pots over winter without their widdle woots freezing—especially if the pots are really big and you line them up against the wall of your home, which being a Philadelphia townhouse, should leak warm air like a sieve. (What we call a metropolitan microclimate.)

But gardeners in your surrounding suburbs—growing in the very same alleged USDA zone 6 as you—would be guaranteed to lose every plant if they left them outdoors. The options are to drag them inside (betcha happy you used that light stuff instead of dirt now!) to a sun room or cold but not freezing garage or basement, or lay them on their sides against a non-South facing wall, cover with leaves and light candles to both Sts. Francis and Fiacre.

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